Rock drill



Jan. 12, 1943. F. M. SLATER 2,307,866

ROCK DRILL Filed Sept. 20, 1941 V [NVENTO'R Fzg-E j l a'emima.

H l 5 ATTORNEY- Patented Jan. 12, 1943 noon mum.

Fred M. Slater, Phillipsburg, N. J., assignor to Ingersoll-Rand Company, New York, N. Y., a corporation of New Jersey Application September 20, 1941, SerialNo. 411,672

8 Claims. (Cl. 121 27) This invention relates to rock drills, and more particularly to rock drills having pressure actuated valve means for effecting the control of the power supply to the percussive element of the rock drill.

One object of the invention is to assure a powerful blow of the piston of the percussive element and a minimum consumption of pressure fluid.

Another object is to effect a rapid action of the percussive element and at the same time reduce the shock and vibration resulting from the action of such element to a minimum.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying this specification and in which similar reference numerals refer to similar parts, 7

Figures 1 and 2 are longitudinal sectional elevations of a rock drill constructed in accordance with the practice of the invention and showing the pressure fluid distributing elements positioned for eflecting the driving of the hammer piston forwardly on its working stroke and rearwardly, respectively.

Referring more particularly to the drawing, 20 designates a rock drill comprising a cylinder 2| and front and back heads 22 and 23 which may be secured to the cylinder in any convenient manner to serve as closures for the ends thereof.

The cylinder 2| is bored to provide a piston chamber 24 for the accommodation of a reciprocatory hammer piston 25 having a stem 26 on its front end that extends slidably through the front head 22. Thus, in the form shown, the piston 25 has a large pressure area 21 on its rearward end and a smaller pressure area 28 on its front end to be subjected to pressure fluid for effecting reciprocatory movement of the piston.

The pressure fluid used for actuating the piston 25 is valved to the ends of the piston chamber by valve mechanism, designated in general by 29 and comprising a valve chest 30 having a bore 3| extending entirely therethrough. On the side of the valve chest is a boss 32 having an opening 33 to accommodate the threaded end of a pressure fluid supply conduit (not shown). A supply passage 34 leads from the opening 33 to the bore 3| in the transverse plane of the opening 33, and a second supply passage 35 leads from the opening 33 to a point near the front end of the bore 3|.

The bore 3| is shown as being of uniform diameter throughout its length and contains bushings 36 and 31 inserted thereinto from the rearward and front ends respectively. These bushings are of such length that whenthey are positioned-in the bore 3| a space 38 exists be tween their inner ends, and in the wall of the cylinder 2! is a passage 39 to afford communication between the space 38 and the rearward end of the piston chamber 24. Each bushing is provided on its outer end with a flange 43- to seat against the adjacent end of the valve Lche'st 30.

A closure is provided for the outer end of the bushing 35 by a plug 4i having a flange 42 that engages the end of said bushing. The outer end of the bushing 31 is likewise closed by a plug,

designated 43, that lies within the bushing 31 and has a shoulder 44 abutting an end of a bushing 45 arranged within the bushing 3l and. seating with its inner end against 'a shoulder 43 in the bushing 31. A plate 41 overlies the outer end of the plug 43 and is clamped thereagainst by bolts 48 extending through the plate 41 and the flange 42 to clamp the plugs 41 and 43 and the bushings 36, 31 and 45 securely in position.

The space in the bushings 35 and 3!v between the plug 4| and the bushing 45 constitutes a valve chamber 49 that communicates with the rear end of the piston chamber through the passage 39 and with the opening 33 through the supply passage 34, the said supply passage 34 being located rearwardly of the space 33 and, therefore, rearwardly of the passage 39.

The valve chamber consists of portions of different diameter, the larger of these, designated 50, is located in the inner end of the bushing 35 on the opposite sides of the supply passage 34.

A portion 5i of slightly smaller diameter than v the portion 50' is located between the portion 53 and the plug 4!, and the'portion of minimum diameter of the valve chamber, designated 52, is located entirely within the bushing 31. An exhaust port 53 in the bushing 3i and the valve chest 30 leads from the portion 52 of the valve chamber to the atmosphere. Within the valve chamber 49 is a reciprocator valve 54 of the spool type which, in the form of the invention shown, serves only-to control the pressure fluid supply for the rearward end of the piston chamber 24. The valve 54 has a head 55 slidable in the portion 52 of the valve chamber and a head 56 lying within the portion 5| of the valve chamber. At the inner end of the latter head is an external flange 51 to slide within the large portion 50 of the valve chamber.

The heads Hand 56 are connected by a stem 58 of comparatively small diameter to assure a large flow area between the heads for the passage of fluid from the supply passage 34 to the passage 39, as well as from the passage 39 to the exhaust port 53.

The pressure fluid serving to actuate the valve 54 to its different controlling positions is valved from the piston chamber 24 to the valve chamber by the piston 25. The cylinder 2| is accordingly provided with a kicker passage 59 that conveys pressure fluid from the piston chamber at a point forwardly of the passage 39 to the rearward end of the valve chamber to act against the rearwardly facing surfaces of the valve constituting, collectively, a pressure surface 60. v

A suitable holding surface 6! is provided on the rearward end of the flange 1'to-be subjected to pressure fluid in the valve chamber for holding the valve stationary in its forward position. The front end of the flange 57 likewise constitutes a holding surface 62 against which pressure fluid acts to hold the valve in the rearmost limiting position. V a

Preferably the head 55 is provided with an external annular groove 63 which, in the rearward position of the valve, communicates with an atmospheric vent 64 in the bushing and the valve chest for exhausting such pressure fluid as may be entrapped in the rearward end of the enlarged portion 55 of the valve chamberafter' the holding surface 5| has moved out of corn; munication with the supply passage 34 during the rearward movement of the valve, and a leak port 65 is formed in the plug 4| to afford constant communication between the rearward end of the valve chamber and the atmosphere. 7 e

The pressure fluid serving to move the Valve rearwardly to the position shown in Figure 1 is also valved to the valve chamber 49 by the piston and flows through a kicker passage 66 opening into the piston chamber at a point forwardly of thekicker passage 59 and into the valve chamber forwardly of the exhaust port 53 and its admission into the valve chamber is controlled by the head 55 of the valve. The head 55 is hollow, having a recess 61, and in the wall of the head. is a port, or ports, 68 to register with the kicker passage E6 in'the forward position of the valve.

Preferably a vent 69 is formed in the valve rearwardly of the port 58 to communicate with the exhaust port 53 for bleeding pressure fluid from the recess 6i to the atmosphere after the valve has been thrown to its rearmost limiting position. The pressure fluid thus admitted into the recess El and into the front end of the valve chamber acts against the forwardly facing surfaces of the head 55, and which surfaces collectively constitute a pressure surface 10, to throw the valve rearwardly. As a preferred arrangement, the inner end of the plug 4| serves as an abutment for the rearward end of the valve 54, and an abutment is provided for the front end of the valve by a stem H on the inner end of the bushing a5 and extending into the recess 61 to engage the bottom thereof.

As will be apparent from the description of the invention so far set forth, the admission of pressure fluid into the rearward end of the piston chamber takes place intermittently and the valve 54 controls only the rearward end of the cylinder. In order to effect the return movement of the piston a separate valve means is provided for the front end of the piston chamber and this valve means operates to maintain a constant charge of pressure fluid in the front end of the piston chamber 24 of a value substantially lower than that of the pressure fluid used for actuating the piston on its working stroke.

The valve serving this function and designated 12 is, in effect, a reducing valve. It is of the reciprocatory type and arranged in a valve chamber 13 consisting of an enlarged portion 14 in the inner portion of the bushing 45 and a reduced portion 15 defined by an annular extension 16 on the inner surface of the plug 43 and extending into the bushing 45: The valve 12 is correspondingly shaped, having a head portion 17 lying in the portion M of the valve chamber and a stem 18 slidable in the reduced portion 15 of' the valve chamber.

The free end of the stem 18 is constantly exposed-to atmospheric pressure maintained in the bottom or outerend of the reduced portion 75 of the valve chamber by a vent 79 extending through the plug 43 and the plate 41.

Theopposite end of the valve constitutes an actuating and holding surface 80 which is constantly subjected to the pressure of the fluid in the'front end'of" thepiston chamber. Such pressure fluid has free access to the surface 80' through a' passage 81' extending from the front end of the piston chamber through thec'ylinder and the bushing 37 and communicating with a port 82 in the'bushing'45that opens intothe inner end of 'the valve chamber adjacent the surface 80.

The opposite end of the head 77 also serves as an actuating and holding area 83 which is smaller in area than the'surface 80 by anamoun't equal to the area of the stem 18'. The'surfa'ce 83 is constantly subjected to pressure fluid conveyed into the enlarged portion !4 of the'valve chamber 13 by the supply passage 35, andin the wall of'the bushing 45intermediate the'en'ds of the enlarged portion 74 'is a port 84' to afford communication between the enlarged portion 14 and the passage 8l. The port 84' is so located that it may be uncovered andcove'red'by the head I! to permit or interrupt the flow of pressure fluid into the front end of the piston chamber.

In order topreven't an undue'increase in the value of the pressure fluid entrapped in the front end of the piston chamber during the forward stroke of the piston the cylinder is provided with a series of chambers 85that are in constant communication with the front end ofthe'pi's'ton chamber 24 through ports 86;

The operation'of the device is as follows: With the hammer piston 25 and the valve elements in the positions shown in Figure 1, and assuming that the supply passages 34 and '35 are in open communication'with the source of pressure fluid supply, pressure -fli'ii'd will' flow from the supply passage 34' through the valve'chamber and the passage same the rearward end of the piston chamber 24"ag'ainst the pressureal'ea 21' to drive the piston forwardly on itsworki'ng stroke. The valve 54 Will beheld rearwardly against the plug 4 l by the pressure fluid flowing across the holding surface 62.

Pressure fluid will, of course, also be'pres'ent the front'end' of the piston chambersince when pressure fluid is admitted into thesup ply passage 35 it will act against the surface 83 of the valve 12 and move said valve into position to establish communication between the supply passage 35 and the passage 8f. The valve 12 will remain in this position'until the pressure fluid in the piston chamber reaches such a value that that acting against the surface 80 of the valve 12 will predominate over the pressure of the fluid acting-against the surface 83 and move the admission of pressure fluid into the front end of the piston chamber.

During the forward movement of the piston A and shortly prior to the delivery of its stroke against the working implement it is intended to actuate the piston will uncover the kicker passage 59. Pressure fluid will then flow from the rearward end of the piston chamber into the corresponding end of the valve chamber against the pressure surface 50 and move the valve 54 forwardly to the position shown in Figure 2.

In the new position of the valve the holding surface 6i will be subjected to the pressure fluid in the supply passage 34 and the valve will be held stationary thereby in its forward limiting position. Also, in this position of the valve the passage 39 will be in communication with the exhaust port 53 and the pressure fluid in the rearward ends of the piston chamber and the valve chamber will then be exhausted to the atmosphere.

As the piston approaches the end of its forward stroke it covers the kicker passage 85 so that no pressure fluid may pass therethrough into the recess 6?, even though the port 68 in the valve is then in registry with the kicker passage 68.

Upon the exhaust of pressure fluid from the rearward end of the piston chamber the fluid in the front end of the piston chamber will act against the pressure area 28 and return the piston to the rearward end of the piston chamber. During movement in this direction the piston will uncover the kicker passage 66 and pressure fluid then flows through the port 63 into the recess 61 against the pressure surface Hi and moves the valve 54 to its initial position.

After the port 68 has been moved out of registry with the kicker passage 66 the pressure fluid in the front end of the valve chamber 49 will act expansively to complete the rearward stroke of the valve. Such pressure fluid will then be entrapped in the front end of the valve chamber 49 but its value will be reduced somewhat by the slight amount of leakage through the vent 69 which will then be in registry with the exhaust port -3, and the pressure acting against the forward end of the valve may then be readily overcome by that admitted into the rearward end of the valve chamber for again throwing the valve 54 forwardly.

As will be readily apparent to those skilled in the art to which the present invention pertains, the value of the fluid constantly present in the front end of the piston chamber will be increased only in a slight degree during the forward stroke of the piston 25 since the space wherein it is compressed is of large volume.

faces 89 and 83 of the valve 12 any desired ratio of pressure acting against the pressure areas 2'8 and 2'! of the piston may be effected.

In practice, however, it has been found that the value of the pressure fluid within the front end of the piston chamber 24 may be very materially reduced below that of the pressure fluid acting against the pressure area 21 for effecting the working stroke of the piston. This feature has been found to be highly desirable in rock drills since it makes possible the use of a pressure area 27 best suited to assure a piston stroke of a desired force Without necessitating an unduly large piston stem in order to maintain the opposed pressure area 28 of such size that the pressure It will, moreover, be obvious that by properly proportioning the surfluid acting thereagainst will not materially reduce the effectiveness of the working stroke of the piston, as is the case in rock drills in which a pressure or actuating area of the piston is constantly subjected to pressure fluid of the same value as that applied to the opposite end of the valve means acting automatically for controlling the flow of pressure fluid into the other end of the piston chamber to maintain a constant pressure therein of a lower value than the pressure of the fluid admitted into the first mentionedend of the piston chamber for returning the piston, opposed pressure surfaces on the first-mentioned valve means subjected alternately to pressure fluid for actuating the said first-mentioned valve means, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

2. A fluid actuated rock drill, comprising a casing having a piston chamber and exhaust con-- duit means for only one end of the piston cham'- ber, a reciprocatory piston in the piston chamber, valve means controlled by the piston for effecting the intermittent intermission of pressure fluid into one end of the piston chamber for actuating the piston in one direction and to control the exhaust conduit means, other valve means moving in response to the pressure in the other end of the piston chamber to maintain a constant pressure therein of a lower value than the pressure of the fluid admitted into the first men-' tioned end of the piston chamber for returning the piston, opposed pressure surfaces on the firstmentioned valve means subjected alternately to pressure fluid for actuating the said first-men-' tioned valve means, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

3. A fluid actuated rock drill, comprising acasing having a piston chamber and exhaust conduit means for only one end of the piston chamber, a reciprocatory piston in the piston chamber, a fluid actuated valve for effecting the admission of pressure fluid into one end of the pis-' ton chamber for actuating the piston in one direction and to control the exhaust conduit means,

a pressure fluid reducing valve acting in response to the pressure in the other end of the piston chamber for controlling the charging of the said other end of the piston chamber with pressure fluid of a lower value than the pressure of the fluid admitted into the first mentioned end of the piston chamber for returning the piston, opposed pressure surfaces on the first-mentioned valve subjected alternately to pressure fluid for actuating the first-mentioned valve, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pres-.-

sure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

4. A fluid actuated rock drill, comprising a casing having a piston chamber and exhaust conduit means for only one end of the piston chamber, a reciprocatory piston in the piston chamber, a fluid actuated valve controlled by the piston for effecting the admission of pressure fluid into one end of the piston chamber for actuating the piston in one direction and to control the exhaust conduit means, another valve acting automatically for admitting pressure fluid into the other end of the piston chamber for constantly chargingsaid other end to return the piston, opposed pressure surfaces on the first-mentioned valve subjected alternately to pressure fluid for actuating the first-mentioned valve, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

5. A fluid actuated rock drill, comprising a casing having a piston chamber and exhaust conduit means for only one end of the piston chamber, a reciprocatory piston in the piston chamber, a fluid actuated valve controlled by the piston for effecting the admission of pressure fluid into one end of the piston chamber to actuate the piston in one direction and to control the exhaust conduit means, another valve for admitting pressure fluid into the other end of the piston chamber for returning the piston and having opposed actuating surfaces one of which is subjected to pressure fluid supply and the other actuating surface to the pressure of the fluid in the said other end of the piston chamber for actuating the last mentioned valve, opposed pressure surfaces on the first-mentioned valve subjected alternately to pressure fluid for actuating the firstmentioned valve, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

6. A fluid actuated rock drill, comprising a casing having a piston chamber and exhaust conduit means for only one end of the piston chamber, a reciprocatory hammer piston in the piston chamber, a valve controlled by the piston for effecting the admission of pressure fluid into one end of the piston chamber to actuate the piston on its working stroke and to control the exhaust conduit means, a pressure fluid reducing valve for effecting the charging of the other end of the piston chamber with pressure fluid of a constant and lower value than the pressure of the fluid admitted into the first said end for returning the piston, an actuating surface on the reducing valve subjected to pressure fluid supply for moving the reducing valve in a direction for admitting pressure fluid into the piston chamber, an opposed actuating surface on the reducing valve of greater area than the first said actuating surface subjected to the pressure of the fluid in the said other end of the piston chamber for moving the reducing valve in a direction to cut off the flow of pressure fluid into the piston chamber,

' opposed pressure surfaces on the first-mentioned valve subjected alternately to pressure fluid for actuating the first-mentioned valve, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

7. A fluid actuated rock drill, comprising a casing having a piston chamber and exhaust conduit means for only one end of the piston chamber, a reciprocatory hammer piston in the piston chamber having an enlarged pressure surface at one end and a reduced pressure surface at the other end, a valve controlled by the piston for effecting the intermittent admission of pressure fluid to one end of the piston chamber to act against the enlarged pressure surface for actuating the piston on its working stroke and to control the exhaust conduit means, another valve moving in response to the pressure in the other end of the piston chamber to maintain a constant pressure against the reduced pressure surface of a lower value than the pressure of the fluid admitted into said one end of the piston chamber for returning the piston, opposed pressure surfaces on the first-mentioned valve subjected alternately to pressure fluid for actuating the first-mentioned valve, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

8. A fluid actuated rock drill, comprising a casing having a piston chamber and exhaust conduit means for only one end of the piston chamber, a reciprocatory piston in the piston chamber, valve means for effecting the intermittent admission of pressure fluid into one end of the piston chamber for actuating the piston in one direction and to control the exhaust conduit means, other valve means acting automatically for controlling the flow of pressure fluid into the other end of the piston chamber to maintain a constant pressure therein of a lower value than the pressure of the fluid admitted into the first mentioned end of the piston chamber for returning the piston, a clearance chamber for said other end of the piston chamber and in constant communication therewith, opposed pressure surfaces on the first-mentioned valve subjected alternately to pressure fluid for actuating the firstmentioned valve, a kicker passage for conveying pressure fluid from the said one end of the piston chamber to one pressure surface, and a kicker passage for conveying pressure fluid of low pressure value from the said other end of the piston chamber to the other pressure surface.

' FRED M. SLATER. 

